Achiote is the musky-flavoured seed of the annatto tree. It is used for both colouring and flavouring food, usually as a base of seasoning pastes for meat and fish dishes. Buy whole seeds when they’re a rusty red color; brown seeds are old and flavourless. Achiote seed is also called annatto which, in its paste and powder form, is used as a colouing agent for margarine and cheese.